Localization of messenger RNA is a conserved form of post-transcriptional regulation in eukaryotes that has been implicated in numerous cellular and developmental processes. Recent research has demonstrated that many mRNAs are enriched on spindle microtubules in Xenopus laevis and human cells. However, the cellular significance of this phenomenon, as well as the molecular mechanisms mediating localization, remain unclear. Proposed experiments will investigate the mechanism and purpose of mRNA localization to spindle microtubules in Xenopus laevis through a combination of biochemical and cytological assays. The first specific aim is to identify potential factors involved in mRNA spindle-localization by biochemically purifying proteins that specifically bind mRNAs identified as being enriched on Xenopus microtubules. The second specific aim is to functionally characterize the purified proteins to identify factors that directly mediate mRNA localization to spindle microtubules. Finally, the third specific aim is to address the cellular significance of mRNA localization to spindles, by investigating the localization and function of proteins translated from microtubule-associated mRNAs. These experiments will provide general insight into the mechanism and purpose of subcellular mRNA localization. PUBLIC HEALTH RELEVANCE: To function properly, cells must localize numerous cellular components to specific subcellular regions, as many components perform a necessary function in one region of the cell but are detrimental if localized elsewhere. As an example, particular messenger RNAs (mRNAs) are known to exhibit defined localization patterns, and recent research has demonstrated that mRNAs are localized to the structure that separates chromosomes during cell division (mitotic spindle) in frog and human cells. This proposal aims to elucidate how and why mRNAs are localized to the mitotic spindle, using experimentally- tractable frog eggs as the model system.